The thread might not be coming off the spool evenly. It might help to increase the top tension to deal with this. It might also be that the thread isn't suitable for sewing machines or for your particular machine.
You can do a quick test by holding say 3 or 4 feet of thread between your hands. Slowly bring your hands together. If the thread twists onto itself it's not suitable for sewing machines. If the thread droops down straight it's fine.
I should add that it may also be that your needles need to be thrown away. If they've been used for a few hours they may simply be too dull. They may also be badly made. The edges of the eyes of inexpensive or "no-name" needles are generally not polished to the same quality level as brand name quality needles and thread simply does not move through the eye at a consistent tension.
Finally, I'm a bit confused by your picture. I believe you are showing both 15 class bobbins and 66 class bobbins. You're not by any chance not using the correct bobbin in the machine?
Last edited by 1.41; 06-17-2022 at 01:50 AM.